Certified GKH Gardening Expert
Rosebushes that do not bloom can be from various reasons. Are your bushes receiving full sun? Lack of sun will stop blooming.
Another issue could be that the original rosebush died and what came up is new canes from the root stock. Sometimes the root stock shoots will bloom but take a few years to do so but will not be the same type or color of bloom as the desired upper part of the grafted rosebush. Thus the best thing to do is to dig out the rosebushes concerned and plant new ones that you want to enjoy.
In other cases the non blooming may be caused by tiny insects that attack new buds in their early stages of development and cause the buds to fall off the bush and thus never bloom. The 3 in 1 fertilizer you use is likely a systemic so it should take care of such problems. Thus I would not think this is the issue here.
Yet another cause can be too high a nitrogen content in the fertilizers and amendments used. Too high a nitrogen content will cause the bushes to produce lots of beautiful foliage but will either cause limited or no blooms depending upon the rosebush.